Field of the Present Invention
The present invention relates to an expander which is a rotary machine used for a refrigeration cycle or the like.
Description of Related Art
Conventionally, liquefied gases such as LNG and LPG are generated, and nitrogen and hydrogen are liquefied to separate them from air, using a refrigeration cycle that uses cold energy when expanding gases such as nitrogen gas by an expander in cooling.
However, as a rotary machine used as the expander, only a centrifugal expander for the expansion of gas having a small flow rate is known, and there is a need for a plurality of the centrifugal expanders when generating the liquefied gas in a huge plant. For this reason, such a rotary machine is not preferable to use for the huge plant in view of an increase in cost, an increase of installing space and maintenance characteristics.
Thus, it is thought to adopt an axial flow rotary machine as the expander so as to enable to cope with the expansion of the gas having a large flow rate in the huge plant and to solve the above-mentioned problems. When the axial flow rotary machine is adopted, a height dimension of a moving blade increases for coping with the large flow rate, and an occurrence of thrust power becomes the problem. However, for example, by adopting a double-flow type structure such as an axial flow turbine disclosed in the following Patent document 1, it is possible to cancel the thrust power, and performance does not decline in this respect.